Quantitative Optical Coherence Tomography Angiography Parameters in Type 1 Macular Neovascularization Secondary to Age-Related Macular Degeneration

Abstract

Purpose: The purpose of this paper was to study type 1 macular neovascularization (MNV) quantitative optical coherence tomography (OCT) angiography (OCTA) features by means of advanced postprocessing analyses.

Methods: We recruited patients affected by naïve type 1 MNV secondary to age-related macular degeneration (AMD) and age-matched controls. All patients underwent ophthalmologic examination and multimodal imaging. They were treated with pro-re-nata anti-VEGF injections. The ensuing follow-up lasted 24 months. Quantitative OCT and OCTA parameters were statistically analyzed to obtain cutoff values able to distinguish two clinically different patient subgroups. Main outcome measures were best-corrected visual acuity (BCVA), central macular thickness, vessel density of superficial, deep and choriocapillaris plexa, vessel tortuosity (VT) of MNV, vessel dispersion of MNV, number of injections, blooding, pigment epithelium detachment, subretinal fluid, photoreceptor elongation, subretinal fibrosis, and outer retinal atrophy.

Results: Ninety-one eyes (91 patients; 49 men; mean age 78 ± 7 years) and 91 control eyes were included. Mean logarithm of the minimum angle of resolution (logMAR) BCVA was 0.46 ± 0.56 at baseline, increasing up to 0.29 ± 0.30 after 2 years of treatment (P < 0.01). The mean number of intravitreal injections was 7.1 ± 2.0 during the first year and 4.5 ± 1.4 during the second year. A baseline VT cutoff of 8.40 detected two patients' subgroups differing significantly in terms of BCVA improvement after 2 years of treatment.

Conclusions: OCTA-based classification of type 1 MNV, performed at baseline, provided useful information in terms of the functional outcome achievable after 24 months of anti-VEGF treatment.

Translational relevance: Quantitative OCTA-based classification of type 1 MNV, performed at baseline, provided useful information in terms of the functional outcome achievable after 24 months of anti-VEGF treatment.

Keywords: age-related macular degeneration; macular neovascularization (MNV); optical coherence tomography (OCT); optical coherence tomography angiography (OCTA); vessel density; vessel dispersion; vessel tortuosity.

Figure 1.

Pipeline for vessel tortuosity calculation. The process includes: MNV binarization through a mean threshold, MNV skeletonization by using “Skeletonize3D” function provided by ImageJ, followed by analysis of the skeletonized image through the “AnalyzeSkeleton” ImageJ pipeline. More details are provided in the text.

Figure 2.

FA and ICGA images in type 1 MNV. FA shows unremarkable changes in the early stage (A), whereas increased filling and leakage phenomena (arrow), including the typical pinpoint aspect (white asterisk), can be observed in the intermediate (B) and late stages (C). ICGA shows increased perfusion defects from early (D) to intermediate (E) and late (F) stages, with plaque aspect of the neovascular network (orange asterisk).

Figure 3.

OCTA images in type 1 MNV. The superficial capillary plexus appears preserved (A), whereas the deep capillary plexus results rarefied (B). A clear neovascular network is reconstructed in (C). Choriocapillaris shows normal morphology in the extra-lesional region, whereas the neovascular lesion causes a masking of the perfusion in the involved region (D). The correspondent segmentation layers on the OCT B-scans are shown in the lower part of the images.

Figure 4.

Line plot of VT values, showing that group 1 (red line) and group 2 (green line) indeed represent two distinct populations of patients affected by type 1 MNV. Moreover, delta BCVA was plotted to highlight how group 1 (blue line) shows an improvement, whereas group 2 (orange line) reveals a deterioration at the end of the follow-up.

Figure 5.

Type 1 MNV case classified as group 1 (VT < 8.40). OCTA clearly reconstructs SCP (A), DCP (B), MNV (C), and CC (D). Baseline features are shown in (E) and (F). After anti-VEGF treatment, exudation was found to be markedly reduced, as was the progression of the outer retinal atrophy at both the 1-year (G, H) and 2-year (I, J) follow-ups.

Figure 6.

Type 1 MNV case classified as group 2 (VT > 8.40). OCTA clearly reconstructs SCP (A), DCP (B), MNV (C), and CC (D). Baseline features are shown in (E) and (F). Exudation was found to have diminished markedly following anti-VEGF treatment. However, the onset and progression of outer retinal atrophy are clearly visible, together with the development of intraretinal cysts associated with progressively deteriorating conditions at both the 1-year (G, H) and 2-year (I, J) follow-ups.